The present invention relates to telescopic sights for firearms and, more particularly, to range-finding and range-compensating features for such a sight.
Present range-finding telescopic sights depend, in general, on a stadia measurement system in which the power adjustment control is manipulated to adjust the size of the target image so as to fill the space between pre-set reticle marks. The range is then indicated by the setting of the power adjustment control. Such systems, obviously, are of use only in variable power sights.
For use in fixed-power sights, it is known to provide both fixed and movable reticles; the movable reticle being manipulated so as to bracket the target therebetween. The range is then indicated by the setting of the reticle adjustment control. Such systems are generally complex and further suffer in that, in high power sights, the magnification of the movable reticle obstructs the view of the target area.
It is, therefore, a primary object of the present invention to provide a telescopic sight which indicates the range of a target of known size and, more particularly, to provide such range-finding capability in a sight of fixed or high power.
It is another object to provide a telescopic sight which compensates for predetermined bullet drop over the target range.
It is yet another object to provide a sight as aforesaid which is sturdy, accurate, and simple to use.
It is a further object to provide such a sight which may be readily adjusted for use with firearms and/or ammunition loads of differring characteristics and for targets of different sizes.
The foregoing objects are achieved by a telescopic sight having first and second reticles fixed, respectively, in the rear and front focal planes, and means for controllably displacing the image of the second reticle, formed in the rear focal plane, so as to bracket the target between the first reticle and the image of the second reticle. The image displacing means is calibrated so as to indicate the range of the bracketed target. More specifically, the image displacing means comprises first screw means threadedly mounted in the sight body tube and operable to pivot the erector tube. There is also provided second screw means operable to rotate the erector tube to compensate for predetermined bullet drop over the target range.